Process for the production of aldehydes and ketones



United States Patent 3,086,994 PROCESS FOR THE PRODUCTION OF ALDEHYDES AND KETONES Jurgen Smidt, Munich-Solln, Walter Hafner, Munich, Reinhard Jira, Munich-Pasing, and J osef Sedlmeier and Alois Maier, Munich, Germany, assignors to Consortium fiir Elektrochemische Industrie G.m.h.I-L, Munich, Germany No Drawing. Filed July 24, 1958, Ser. No. 750,570

Claims priority, application Germany Aug. 1, 1957 8 Claims. (Cl. 260-597) The present invention relates to an improved process for the production of carbonyl compounds by the catalytic oxidation of olefinically unsaturated hydrocarbons employing an aqueous catalyst solution containing platinum metal compounds and salts of multivalent metals. In particular, the process according to the invention concerns the production of acetaldehyde from ethylene, as well as ketones and higher aldehydes from hydrocarbons containing one or more double bonds in which the number of carbon atoms in the carbonyl compound produced is the same as that in the hydrocarbon used as a starting material.

In application Serial No. 744,011, filed June 23, 1958, and application Serial No. 750,107, filed July 22, 1958, processes for the production of carbonyl compounds are described in which olefines or olefine-oxygen mixtures are brought into intimate contact with aqueous solutions of platinum metal compounds which also contain salts of multivalent metals.

In the absence of oxygen or in the presence of insufiicient quantities of oxygen, the metal salts in the catalyst solution are reduced to a lower, inactive oxidation step so that a special reaction step is required for the oxidation of the catalyst solution in order that its activity be maintained.

In another application, Serial No. 738,040, filed May 27, 1958, now abandoned, a process is described in which the reoxidation of the catalyst solution is carried out with oxygen expediently at elevated temperature after removal of the carbonyl compounds formed and in the ab sence of hydrocarbons.

According to the invention it has been found that such reoxidation can be substantially improved by the simultaneous. action of oxygen and oxidizing nitrogen-oxygen compounds. The use of a combination of oxygen and nitrogen-oxygen compounds for the reoxidation renders it possible also to reconvert such salts, which are normally only slowly oxidized with oxygen alone, rapidly to their active oxidation step. The use of such salts which are only slowly reoxidizable with oxygen alone, for example, the sulfates, however, provides certain advantages in the production of carbonyl compounds from olefines. For instance, the carbonyl compound formation takes place more rapidly, often with higher yields, than, for example, when halides are used.

The carbonyl compound formation can be carried out by bringing olefines or olefine-oxygen mixtures into intimate contact with aqueous catalyst solutions containing platinum metal compounds and multivalent salts at temperatures up to 200 C., preferably between 50 and 150 C. Relatively low quantities of the platinum metal compounds, preferably about 2-20 g. per liter of solution, are employed Whereas larger quantities or higher concentrations of salts of multivalent metals are employed. The ratio of platinum metal to multivalent metal in such solutions can be up to 1:100 and above.

The compounds of the platinum metals, particularly those of palladium and rhodium, are catalytically active. The type of non-metallic component of such platinum metal compounds is only of secondary importance as long 3,086,994 Patented Apr. 23, 1963 as extremely strong complex formers, such as cyanide ions, or precipitating agents, such as sulfide ions, are not concerned. The halides, sulfates, phosphates, acetates or corresponding complexes are, for example, suitable.

The salts of copper and iron are particularly suited as the multivalent metal salt component of the catalyst solution. Other multivalent metal salts whose oxidation potential is above that of the platinum metal compound employed can also be used. Preferably, ferric sulfate is employed as the multivalent metal salt.

The carbonyl compound formation is carried out in an acid to neutral solution.

The reoxidation of the catalyst solution with oxygen and nitrogen-oxygen compounds is effected after removal of the carbonyl compounds formed and in the absence of olefines or other hydrocarbons. Nitrogen oxides and nitrio acid are suited as the oxidizing nitrogen-oxygen compounds employed in combination with the oxygen. It is especially advantageous if an excess of oxidizing nitrogenoxygen compound, with reference to reduced portions of the catalyst solution in the part of the catalyst solution being reoxidized, is maintained in the oxygen and nitrogenoxygen compound mixture employed for the reoxidation. i

In order to attain usable oxidation efiiciencies, it is neither necessary to employ especially high concentrations of nitrogen-oxygen compounds or to employ stoichiometric quantities of the nitrogen-oxygen compounds with reference to the reduced portions of the entire catalyst solution. It is only essential that the nitrogen-oxygen compounds are always present in the portion of the catalyst solution being reoxidized in excess of the reduced portions contained in such portion of catalyst solution. This, for example, can be achieved by adjusting the velocity at which the catalyst solution is supplied to the action of oxygen and nitrogen-oxygen compounds to a velocity corresponding to the progress of the oxidation. The continuous presence of sufiicient quantities of oxygen has the effect of maintaining the original quantity of oxidizing nitrogen-oxygen compounds supplied by continuous reformation of such nitrogen-oxygen compounds during the reaction. It is therefore possible in view of this constant regeneration of the nitrogen-oxygen compound to carry out the regeneration of the catalyst solution with a quantity of nitrogen-oxygen compounds which is considerably less than the stoichiometric quantity required for reoxidation of all of the reduced portions of the catalyst solution taken as a whole over a period of time provided suitable adjustment of the rate of supply of the used catalyst solution to the action of the oxygen and nitrogenoxygen compounds is maintained. Even when working under such conditions the reoxidation is rapid and complete.

The treatment of the used catalyst solution with the oxygen and nitrogen-oxygen compounds can take place at ordinary room temperatures. It is, however, preferable to employ elevated temperatures, for example, in the range of 50 to C. The pressures employed are selected with regard to the temperatures used. Pressures of, for example, 1 to 50 atmospheres can be used.

The reoxidized catalyst solution is then admixed with a small excess of a further quantity of used catalyst solution with respect to the quantity of nitric acid or nitrogenoxygen compounds still contained therein and passed through a filled tower and treated with air or steam to free it from nitrogen oxides before being reused as the catalyst for the production of carbonyl compounds.

The process according to the invention involves a reaction between phases of only limited miscibility. As a consequence, all measures which provide for intensive intimate contact of the phases or increase the miscibility of the phases promote the reaction. Intensive contact can be attained by mechanical measures such as stirring,

a sence shaking, vibrating, spraying and the like and chemical measures which favor the formation of large surfaces. In order to increase the miscibility, blending agents such as acetic acid or dioxane can be added. The solubility of gaseous reactants can be increased by employing superatmospheric pressures. The process according to the invention can be carried out at any desired pressure, preferably, however, a pressure within the range of 1 to 50 atmospheres is employed.

The time during which the olefines and the carbonyl compounds formed are in contact with the aqueous catalyst solution can amount from a few seconds to several hours. The time of contact depends upon the reactivity of the olefine, the composition of the catalyst solution, the pressure and temperature, as well as the type of oxidizing agent employed. The lower olefines react rela tively rapidly, while longer reaction times are required for higher olefines. Palladium compounds act very quickly whereas the compounds of the other platinum metals are considerably slower in their action. Increases in pressure and temperature accelerate the reaction. An upper limit for the time of contact is provided in the case of easily oxidizable and acid sensitive carbonyl compounds, especially when higher temperatures are employed and when strong oxidizing agents are employed. The permissible periods of contact can easily be determined for each individual case by determining the yields obtained.

Olefinically unsaturated hydrocarbons are generally suitted as starting materials. The reaction does not occur only in the case of strongly sterically hindered compounds such as tetraphenyl ethylene.

There also are no special requirements with regard to the purity of the hydrocarbons employed as starting materials. Only acetylene, hydrogen sulfide and its derivaties lower the activity of the catalyst solution and decrease the conversion.

The process according to the invention can be carried out in all apparatus for reacting gases, liquids or solids wtih each other, such as, for example, trickle or spray towers, filled columns, stirring vessels and the like. Naturally, the portions of such apparatus coming into contact with the strong oxidizing acid solutions must be of corrosion resistant material. Suitable corrosion resistant materials, for example, are enamel, glass, porcelain, stoneware, synthetic resins, rubber, titanium, tantalum and Hastelloy.

The carbonyl compounds produced can be recovered in various ways. Easily volatilized compounds, insofar as they are carried out with the non-converted gas stream, can be separated out by condensation or scrubbing. The compounds retained in the catalyst solution can be recovered by distillation. Difficultly volatile compounds can be recovered by liquid-liquid extraction, separation or filtration. By-products, such as organic acids, are only produced in small quantities and easily can be separated. The yield of carbonyl compounds on an average is 90% and over.

The following examples will serve to illustrate a number of embodiments of the process according to the invention:

Example 1 10 liters per hour of a gas mixture consisting of 79 vol. percent of ethylene, 16 vol. percent of methane and vol. percent of N were passed upwardly through a trickle tower filled wtih Raschig rings countercurrently to a downwardly trickling catalyst solution supplied at a rate of 2 liters per hour. The aqueous catalyst solution contained 17.8 g. of PdCl 281 g. of Fe (SO .9H O 17 g. of CuCl .2H O and 100 g. of H 80 per liter. A reaction temperature of 95 C. was maintained in the tower. The acetaldehyde formed together with a little entrained water were separated from the residual gases by cooling. Two-thirds of the catalyst solution running out of the tower, after addition of 80 g. of 30% HNO were treated 4 in a second trickle tower at 95 C. with a strong stream of air. The catalyst solution running out of the latter tower was united with the residual one-third of the catalyst solution running out of the first tower and then again treated with air in a third tower to remove the excess nitric acid contained therein. The solution flowing from the bottom of the third tower was recycled to the first tower.

Example 2 thylene was passed countercurrently to a catalyst solution containing 17.8 g. of PdCl .281 g. of

and 100 g. of H per liter in a trickle tower maintained at a temperature of 95 C. 3.44 liters per hour of catalyst solution were withdrawn from the tower. This solution in which 80% of the trivalent iron contained in the original solution had been converted to divalent iron was continuously freed from acetaldehyde by distillation.

In order to initiate the oxidation of the used catalyst solution, 1.2 liters of the aldehyde free catalyst solution were slowly introduced into a vessel provided with a stirrer containing 16.8 cc. of nitric acid (300 g. HNO /liter) standing under oxygen at a superatmospheric pressure of 50 mm. Hg. The temperature in the vessel was maintained at 60 C. After the oxidation was initiated, 2.4 liters per hour of the used catalyst solution together with 33 cc. per hour of nitric acid (300 g. HNO /liter) were continuously supplied to the vessel. The same quantity of completely reoxidized catalyst solution was continuously withdrawn and treated, after being combined with the remaining 1.04 liters of non-reoxidized catalyst solution, in a filled tower countercurrently with air and steam for the removal of the nitrogen oxides and nitric acid contained therein. After removal of the nitrogen oxides and nitric acid, the catalyst solution is again recycled for reaction with ethylene. The nitrogen-oxygen compounds which were blown out of the solution were converted to nitric acid with air and water.

Example 3 The reaction between the catalyst solution of Example 2 with ethylene was carried out in such a manner that only about 10% of the trivalent iron contained therein was reduced to divalent iron by appropriate selection of the velocity of the ethylene, the rate of supply of the catalyst solution and the height of the tower. 3 liters per hour of used catalyst solution resulted.

The initiation of the oxidation of the used catalyst solution was effected as in Example 2 with the slow introduction of 1 liter of the used aldehyde free catalyst solution into 1.4 cc. of nitric acid (300 g. I-INO liter). After initiation of the oxidation, this mixture was supplied to a reaction tower maintained at C.

2 liters per hour of the used catalyst solution together with 2.8 cc. of nitric acid were then supplied to the bottom of such tower while simultaneously supplying an excess of oxygen to the bottom of such tower. The reoxidized solution flowed out of the top of the tower.

The necessary excess of nitrogen-oxygen compounds is maintained in the reaction tower by the oxygen which passes upwardly through the tower concurrently with the catalyst solution. The excess oxygen leaving the top of the tower together with the nitrogen-oxygen compounds entrained was recycled to the bottom of the tower after replenishing the quantity of oxygen consumed, to provide an oxygen cycle for the reoxidation.

Example 4 The conversion of ethylene with the catalyst solution was carried out as described in Example 2. A filled tower in which a downwardly directed stream of air was maintained was employed for reoxidation of the used catalyst solution. The used catalyst solution was supplied to the top of the tower as well as to four further locations distributed along the height of the tower. 460 cc. of the used catalyst solution together with 37 cc. of nitric acid (300 g. HNO /liter) were supplied per hour to the upper end of the tower. As soon as the oxidation was initiated, 460 cc. per hour of the used catalyst solution were introduced at each of the other four locations. The nitric acid supplied to the top of the tower along with the used catalyst solution is constantly regenerated by the concurrently flowing stream of air, so that an excess of nitric acid is always present at all of the locations where the used catalyst solution is supplied. A reaction temperature of 95 C. was maintained in the tower. 2.3 liters per hour of completely reoxidized catalyst solution were withdrawn from the bottom of the tower, mixed with the remaining 1.14 liter of used catalyst solution and treated to remove the nitrogen oxygen compounds contained therein as described in Example 2 before reuse.

Example 5 1 liter of an aqueous solution containing 4 g. PdCl 120 g. Fe (SO -9 H 0 and 100 g. of H 80 was boiled together with 25 g. of l-nonene in a column provided with a vibr-omixer and a reflux condenser. After about 3 hours the n-heptyl methyl ketone which was formed was blown ofi with steam. The yield was 89%. The residual acidic solution in which about 60% of the trivalent iron had been converted to divalent iron was reoxidized as described in Example 2. In all, 3 cc. of concentrated nitric acid were required therefor.

We claim:

1. In a continuous process for the production of carbonyl compounds selected from the group consisting of aldehydes and ketones by the catalytic oxidation of an olefinically unsaturated compound, the steps of (1) intimately contacting an olefinieally unsaturated hydrocarbon with an aqueous catalytic solution of a catalytically active inorganic salt of a metal of the platinum group and containing a multivalent metal salt selected from the group consisting of iron and copper salts and mixtures thereof at temperatures up to 200 C. to produce a carbonyl compound from said olefinically unsaturated hydrocarbon containing the same number of carbon atoms as said olefinically unsaturated hydrocarbon, (2) separating the carbonyl compound produced from the used catalyst solution, (3) contacting said used catalyst solution in the absence of hydrocarbons with oxygen and nitric acid to regenerate such catalyst solution and (4) recycling such regenerated catalyst solution to step (1) of the process,

2. The process of claim 1 in which the quantity of platinum metal salt in such solution is 2 to 20 grams per liter of solution and the concentration of the multivalent metal salt in such solution is greater than that of the platinum metal salt.

3. The process of claim 1 in which said platinum metal salt is a palladium salt.

4. The process of claim 1 in which the multivalent metal salt is an iron salt.

5. The process of claim 1 in which the treatment of the used catalyst solution with oxygen and nitric acid is carried out at temperatures between and C. and at pressures of l to 50 atmospheres.

6. The process of claim 1 in which a stoichiometric excess of nitric acid, with reference to the reduced components contained in that portion of the used catalyst solution being regenerated, is maintained during the regeneration.

7. The process of claim 6 in which a stoichiometric quantity of oxygen is employed during such regeneration to maintain such excess of nitric acid.

8. The process of claim 6 in which the regenerated catalyst solution is mixed with a further quantity of used catalyst solution which is in excess stoichiometrically with respect to the quantity of nitric acid still contained in the regenerated catalyst solution and contacted with a gas selected from the group consisting of air and steam to remove nitrogen oxides contained therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,999,620 Van Peski et al Apr. 30, 1935 2,523,686 Engel Sept. 26, 1950 2,614,125 Detling Oct. 14, 1952 2,690,457 Hackmann n Sept. 28, 1 954 FOREIGN PATENTS 767,409 Great Britain r Feb. 6, 1957 280,712 Great Britain Nov. 24-, 1927 713,791 Germany Nov. 14, 1941 891,209 France Nov. 29, 1943 OTHER REFERENCES Phillips: Amer. Chem. Iour., vol. 16, pp. 255-77 (pp. 261 and 265-72 relied upon), 1894.

Chatt: Chem. Abstracts, vol. 48, p. 5067 (1954). 

1. IN A CONTINUOUS PROCESS FOR THE PRODUCTION OF CARBONYL COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF ALDEHYDES AND KETONES BY THE CATALYTIC OXIDATION OF AN OLEFINICALLY UNSATURATED COMPOUND, THE STEPS OF (1) INTIMATELY CONTACTING AN OLEFINICALLY UNSATURATED HYDROCARBON WITH AN AQUEOUS CATALYTIC SOLUTION OF A CATALYTICALLY ACTIVE INORGANIC SALT OF A METAL OF THE PLATINUM GROUP AND CONTANING A MULTIVALENT METAL SALT SELECTED FROM THE GROUP CONSISTING OF IRON AND COPPER SALTS AND MIXTURES THEREOF AT TEMPERATURES UP TO 200*C. TO PRODUCE A CARBONYL COMPOUND FROM SAID OLEFINICALLY UNSATURATE HYDROCARBON CONTAINING THE SAME NUMBER OF CARBON ATOMS AS SAID OLEFINICALLY UNSATURATED HYDROCARBON, (2) SEPARATING THE CARBONYL COMPOUND PRODUCED FROM THE USED CATALYST SOLUTION, (3) CONTACTING SAID USED CATALYST SOLUTION IN THE ABSENCE OF HYDROCARBONS WITH OXYGEN AND NITRIC ACID TO REGENERATE SUCH CATALYST SOLUTION AND (4) RECYCLING SUCH REGENERATED CATALYST SOLUTION TO STEP (1) OF THE PROCESS. 